As any pet owner knows, the more food that goes into an animal's mouth, the more wastes that eventually spew out the other end. The bigger the animal, the bigger its appetite. So imagine the volumes of manure—often tainted with germs—that farmers must manage for even a small feedlot with perhaps 3,500 head of cattle.

Ordinarily, beef producers house their animals in pens—some the size of football fields or larger. They're designed to leave each animal about 80 square feet of space. Cattle was...